Linux

Linux Basic Commands You Should Know

In this Blog, We will be discussing some important Linux commands.

Basic Linux Commands
• File Handling
• Text Processing
• System Administration
• Process Management
• Archival
• Network
• File Systems
• Advanced Commands

Sources to learn commands??

Primary – man(manual) pages. 

  • man <command>shows all information about the command.
  • ­­<command> –help ­ shows the available options for that command.

Secondary – Books and Internet.

File Handling commands

  • mkdir – make directories Usage: mkdir [OPTION] DIRECTORY… eg. mkdir geekycodes
  • ls – list directory contents Usage: ls [OPTION]… [FILE]… eg. ls, ls ­l, ls geekycodes
  • cd – changes directories Usage: cd [DIRECTORY] eg. cd geekycodes
  • pwd ­ print name of current working directory Usage: pwd
  • vim – Vi Improved, a programmers text editor Usage: vim [OPTION] [file]… eg. vim file1.txt
  • cp – copy files and directories Usage: cp [OPTION]… SOURCE DEST eg. cp sample.txt sample_copy.txt cp sample_copy.txt target_dir
  • mv – move (rename) files Usage: mv [OPTION]… SOURCE DEST eg. mv source.txt target_dir mv old.txt new.txt
  • rm ­ remove files or directories Usage: rm [OPTION]… FILE… eg. rm file1.txt , rm ­rf some_dir
  • find – search for files in a directory hierarchy
  • Usage: find [OPTION] [path] [pattern] eg. find file1.txt, find ­name file1.txt
  • history – prints recently used commands Usage: history

Pattern

A Pattern is an expression that describes a set of strings that is used to give a concise description of a set, without having to list all elements. eg. ab*cd matches anything that starts with ab and ends with cd etc.

ls *.txt – prints all text files

Text Preprocessing

  • cat – concatenate files and print on the standard output Usage: cat [OPTION] [FILE]… eg. cat file1.txt file2.txt
  • cat ­n file1.txt • echo – display a line of text Usage: echo [OPTION] [string] … eg. echo I love India echo $HOME
  • grep ­ print lines matching a pattern Usage: grep [OPTION] PATTERN [FILE]… eg. grep ­i apple sample.txt
  • wc ­ print the number of newlines, words, and bytes in files Usage: wc [OPTION]… [FILE]… eg. wc file1.txt wc ­L file1.txt

Linux File Permissions

  • sort – sort lines of text files.

Usage: sort [OPTION]… [FILE]…

eg. sort file1.txt

sort ­r file1.txt

  • 3 types of file permissions – read, write, execute
  • 10-bit format from ‘ls ­l’ command
  • 1 2 3 4 5 6 7 8 9 10
  • file type owner group others
  • eg. drwxrw­r­­ means owner has all three permissions,
  • group has read and write, others have only read
  • permission
  • read permission – 4, write – 2, execute ­1

eg. rwxrw­r­­ = 764
673 = rw­rwx­wx

System Administration

  • chmod – change file access permissions Usage: chmod [OPTION] [MODE] [FILE] eg. chmod 744 calculate.sh
  • chown – change file owner and group Usage: chown [OPTION]… OWNER[:[GROUP]] FILE… eg. chown remo myfile.txt
  • su – change user ID or become super­user

Usage: su [OPTION] [LOGIN]

eg. su remo, su

  • passwd – update a user’s authentication tokens(s)

Usage: passwd [OPTION]

eg. passed

  • who – show who is logged on

Usage: who [OPTION]

eg. who , who ­b , who ­q

Process Management

  • ps – report a snapshot of the current processes Usage: ps [OPTION] eg. ps, ps ­el
  • kill – to kill a process(using signal mechanism) Usage: kill [OPTION] pid eg. kill ­9 2275
  • bg – make a foreground process to run in background                        Usage: type ‘ctrl+z’  and then ‘bg ‘  
  • fg – to make background process as foreground process                      Usage: fg [jobid]
  • jobs – displays the names and ids of background jobs                         Usage: jobs

Archival

  • tar – to archive a file Usage: tar [OPTION] DEST SOURCE

eg. tar ­cvf /home/archive.tar /home/original tar ­xvf /home/archive.tar

  • zip – package, and compress (archive) files

Usage: zip [OPTION] DEST SOURCE eg. zip original.zip original.

  • unzip – list, test, and extract compressed files in a ZIP archive

Usage: unzip filename

eg. unzip original.zip

Networking

  • ssh – SSH client (remote login program)

“ssh is a program for logging into a remote machine and for executing commands on a remote machine”. Usage: ssh [options] [user]@hostname. eg. ssh ­X guest@10.105.11.20

  • scp – secure copy (remote file copy program) “scp copies files between hosts on a network”

Usage: scp [options] [[user]@host1:file1] [[user]@host2:file2]

eg. scp file1.txt guest@10.105.11.20:~/Desktop/

File Systems

  • fdisk – partition manipulator. eg. sudo fdisk ­l
  • mount – mount a file system. Usage: mount ­t type device dir. eg. mount /dev/sda5 /media/target
  • umount – unmount file systems. Usage: umount [OPTIONS] dir | device… eg. umount /media/target
  • du – estimate file space usage Usage: du [OPTION]… [FILE]… eg. du
  • df – report filesystem disk space usage Usage: df [OPTION]… [FILE]… eg. df
  • quota – display disk usage and limits Usage: quota [OPTION] eg. quota ­-v.

Editor commands

  • kate – KDE Advanced Text Editor Usage: kate [options][file(s)] eg. kate file1.txt file2.txt • vim – Vi Improved, a programmers text editor Usage: vim [OPTION] [file]… eg. vi hello.c
  • gedit ­ A text Editor. Used to create and edit files. Usage: gedit [OPTION] [FILE]. eg. gedit

Advanced Commands

  • reboot – reboot the system. Usage: reboot [OPTION]. eg. reboot
  • poweroff – power off the system. Usage: poweroff [OPTION]. eg. poweroff.
  • sed ­ stream editor for filtering and transforming text. Usage: sed [OPTION] [input­file]… eg. sed ‘s/love/hate/g’ loveletter.txt
  • awk ­ pattern scanning and processing language. eg. awk ­F: ‘{ print $1 }’ sample_awk.txt
  • find ­ search for files in a directory hierarchy. Usage: find [OPTION] [path] [pattern]. eg. find ­name file1.txt
  • locate – find or locate a file.Usage: locate [OPTION]… FILE…eg. locate file1.txt

Suggested Material

  • The UNIX Programming Environment by Kernighan and Pike (Prentice-Hall)
  • Your UNIX: The Ultimate Guide by Sumitabha Das.

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